Tensioning mechanism for endless webs



Oct. 6,` 1959 E. w. REID 2,907,450

TENSIONING MECHANISM FOR ENDLESS WEBS amc W. Ram

ATToQNPlS Oct. 6, 1959 E. w. REID TENsIoNING MECHANISM FOR ENDLEss WEBS Filed Dec. 17, 1957 2 Sheets-Sheet 24 INVENTQR Eme W. Rmb

4United States Patent Oliice Patented Oct. 6, i959V TENSIONING MECHANISM tFoa ENDLnss WEBS ric William Reid, Earley, Reading, England, assignor to The Keelavite Company Limited, Coventry, England,

aBritish company l., Application December 17, 1957, Serial No. 703,351

11 Claims. (cl. 19s20s) This invention relates to tensioning mechanism for endless webs of the kind used to convey material and is particularly but not exclusively applicable to the wire webs used in paper-making machinery and onto which the pulp is discharged so that as the web travels this pulp is, gradually `dried and is removed as a strip at the delivery end ofthe wire. l

\ The form of tensioning mechanism with which the invention is concerned is that in which a jockey pulley which may be spring-pressed, hydraulically pressed, or weight operated, acts on the return (i.e. the underneath) half ofthe wire to maintain the desired tension in the wire, While one another roller, over which the wire also travels is adjustable, to enable the jockey roller to be maintained as far as possible in an approximately predetermined position relative to the wire, as isnecessary if it is to operate satisfactorily `to maintain the required tension. 1 `For convenience herein the roller which is adjustable to maintain the position of the jockey roller at approximatelyfthe desired position in spite of stretching of the Wire will herein be referred to as theadjustable roller.

adjustable rollers to remove the tension freni the web: An overriding control may b provided for rendering' the automatic relay mechanism inoperative when the manually operable means are in operation. The overriding control may comprise a cut-oli valve: between the reversible hydraulic motor and the relay control valve. The cut-off valve is preferably hydraulically operated by pressure derived from a solenoid-operated auto-control valve, means being included for raising the jockey and adjustable rollers hydraulically by pressure derived through a master valve, the solenoid of the `solenoid-operated auto-control valve being in series with a cut-out switch, and the master valve -being adapted when actuated to supply the raisingimean's to operate the switch so as to cause the solenoid to actuate the auto-control valve and' hence the cut-oli valve to stop the hydraulic motor.

The invention may be carried into practice in various ways but one specilic embodiment will now be described byway of example with reference to the accompanying drawings, in which Figure 1 shows the general arrangement of a paper making machine wire web incorporating a jockey roller roller 4 and over three lixed rollers, 5, 6 and 7 and isY and adjustable roller in accordance with the invention, and

Figure 2 shows -diagrammatically the electrical and hydraulic control and operating circuits.

ln the construction shown in Figure l the wire 1, has an upper run which is supported substantially at and passes around two main rollers 2 and 3. The underneath `or return run of the wire passes under one tixed acted upon at a point between the rollers 5 and 6 bya According to the invention tensioning mechanism for I anendless web includes a jockey roller biassed onto the web to control its tension, an adjustable roller bearing en the Web at another point, and control means by which movement of the jockey roller out of a predetermined position relative to the web due to changes in the length of the web causes automatic operation of relay mechanism to move the adjustable roller relative to the web in such a direction as to adjust the web in a manner to restore the jockey roller to its predetermined position.

Thus if due to stretching of the web the jockey rollersupply to the motor is under the control of a relay control valve under the direct control of the jockey roller. For example the support for the jockey roller mayl carry a cam which operates the relay control valve, which cam `it will be understood is automatically moved so as to render the valve inoperative when as a result of the desired adjustment having been made the jockey roller has been restored toits correct position.

In `one preferred arrangement according to the in vention the jockey `roller is carried on the end of a pivoted supporting arm. Preferably the jockey f roller isubiassed` onto the` web by a Weight. Conveniently manual means is provided for raising both jockey and" jockey roller 8 carried on an arm 9 and pivoted at l0 to the frame of the machine, and is acted upon at a point between the rollers 2 and 7 by an adjustable roller 11 mounted upon an arm 12 pivoted to the frame at 13.

As will be seen in both ligures the arm 9 on which the jockey roller 8 is carried is formed integral with a further arm 17 which is connected to the slotted end 18 of a piston ro-d 19 carrying lat its other end a double acting piston 20 within a hydraulic cylinder 21 pivoted to the frame` about a pivot at 22. The arm 9 carries an adjustable weight 14 by which the tension to be applied by the roller 8 can be set. During normal operation the endf of the arm 17 can slide in the slotter end 1S ofH the piston rod 19, but as will be described in detail later the arm 9 can be lifted clear of the wire to the upperof thedotted positions shown by downward movement of the piston 1'9. The arm 12 carrying the adjustable roller 11 is provided with a quadrant 23 engaged by a pinion 24which, through a gearbox 25 can be rotated in either direction by a reversible hydraulic motor 26 as shown in Figure 2. As shown in Figure l a brake 27 is normally applied by a spring 28 to the shaft of thepinion 24 but is capable of being released by hydraulic pressure acting on one face of a piston 2 9 disposed within a cylinder` 30 as diagrammatically shown in Figure l. The brake is also shown in Figure 2 but has been displaced from the pinion shaft for clarity and ease of' showing the circuits.

As shown in Figure 2 the arm 9 carrying the jockey roller 8 also carries` a cam 41 arranged to act on a roller 42 f,on an adjustable tappet 43 whichin turn., is arranged to act upon the spring pressed piston of a hydraulic valve 44, which is of well `known type and is shown somewhat diagrammatically, as are other valves to be described shortly. It will be seen that the valve 44 has an inlet 44A, two outlets 44B and 44C and an exhaust connection 44D. The inlet `44A is connected to a pressure line 45 whilst the exhaust connection l44D is connected to an exhaustline 46. For convenience where a valve connects-one `passage to another for the flow lof fluid under pressure, it will hereinafter be referred to as the passage of pressure across the valve.

The two outlets 44B and 44C are connected by means of lines 47 and 48 to inlets 49A and 49D respectively of a pressure operated motor-control valve 49. This valve isspring centred to a shut-off position, but is normally moved to the left bypressure applied to the inlet 49G, to place inlet 49A in communication with outlet 49B and inlet 49D in communication with outlet 49C. These two outlets 49B and 49C are connected, by lines 55 and 56 respectively, tothe hydraulic motor 26.

The position of the adjustable roller is automatically governed by the position of thejockey roller 8 in the following way. j

As thejockey roller 8 rises or falls it actuates the-cam 41 to raise or lower the piston of the valve 44. Assuming, for example, that the wire of the paper making machine stretches, the jockey roller 8 will fall and hence the cam will be rotated to permit the piston of the valve 44 to be spring biassed downwards and place the inlet 44A of the valve in communication with the outlet 44C so that pressure passes across the valve 44 and along the line 48. It will be assumed that the valve 49 is pressure operated tothe open position by pressure applied tot the inlet 49G although the details of the manner in which this is effected will be described later.

Accordingly the pressure in the line 48 passes across the motor-control valve 49 to the outlet 49C-and hence to the line 56 which is in communication with thatl sideof the motor 26 which will cause'it to drive the gear b'ox and pinion in such a direction as to lower the adjustable roller 11 to take up the slack in the wire. Such take-up of the wire of course raises the jockey roller Sto-a datum position at which the valve 44 is closed and 'hence stops the motor.

If for some reason the jockey roller is raised during operation of the machine, for instance by shrinkage' of the wire, to a position above the datum position the valve 44 will be moved to a position at which the inlet 44A and outlet 44B of the valve 44 are in communication causing the motor 26 to operate in the reverse direction by pressure appliedV through line 47 across the valve 49 and through the line 55. Hence the adjustable roller in this instance will be raised by the pinion 24 and quadrant 25 to slacken the wire until the jockey roller is restored to its datum position. i

As has been mentioned the automatic operation of the apparatus is under the control of the motor-control valve 49 which is normally held open against its centering spring by pressure'applied to its right hand end or inlet 49G. This pressure is derived from the outlet 50B of an autocontrol valve 50 having its inlet 50A connected to the main pressure line 45. This valve is springacentred to a closed position but normally held in an open position by a solenoid S in series with three normally closed limit switches 51, 52 and 53.

It will-be seen that the lim-it switch Slis placed above Vthe arm 9 of the jockey roller 8 so that it will be openedV if the arm should be raised lto the Ialmost horizontal position shown in dotted lines. The two limit switches 52 and 53 are placed at the desired upper and lower limits of movement of the 'arm 12 ofthe adjustable roller 11.l Thus if any one of the three limit switches 51 to 53 should be opened by the appropriate roller arm the solenoidSS Will be vopcn-circuited and the auto-control -valve 50 returned to its central closed position. Such movementouts off the control pressure to the inlet 49G 'of the motor control valve 49 which is accordingly centred( by its spring lcompletely Vit willv be appreciated that the jockey roller 3 has to be raised out of contact withpthe wire and this is done hydraulically by the piston rod 19.

Pressure for raising or lowering the roll 8 by the piston 19 is `derived from a manually operated control valve 60 which connects either of its outlets 60C or 60B with its inlet 60A according to the position of its operating lever 61. Pressure to `the inlet 60A is derived from a master control 70 via `a pressure line 71 and sub-line '72.

It will be noticed that the master control 70 is so positioncdasfto openthe-li'rnit switchzSl when it is operated to supply the control valvetl. `Accordingly as'so'on as the control valve 60 is supplied with'pres's'lr'e, to permit operationof the. piston 19 to raise the roll 8, the automatic control of the apparatus is stopped since the circuit to the solenoid S5`and hence'the pressureto the valve 49 will be interrupted by opening of the limit switch 51.

Thus there is no possible danger that the raising of the piston 19 wwill result in automatic variation in-position'of Y the adjustable roll 11. ,Y

`(b) Raising 0f adjustable roller I1 For wire changing it will also be necessary -to raise the roller A11 to a position at which it is entirely clear of the wire and hence beyond the limit switch 52. v

This ismanually controlled by a two-Way control switch 80 having'one :pair of contacts 81 in series with also'lenoid 53 of a'further control valve 90, and an upper limit v switch 82.

` of the valve 90, and the lower limitV switch 53. Thusas the jadjustable roller is raised or lowered (in a manner tobe'described shortly) the solenoids S3fan'd S4c`an b energised by operation of theswitch so lo'ng as'th'eir respective limit switches 82 and53 are closed. Assfoon as the roller arm 1.2 reaches its uppermost or lowestlpsition the appropriate limitswitch'will be opened and so prevent further energis'ation of the associatedsolenoid.

The valve nhas an inlet`9tlA connectedtoithepressure line 71 from the master valve 70, and hence, as soonas the valve 7i) is operated, pressure will -be supplied tothe valve inlet 90A. Such pressure is communicated Vacross the valve to one or other of the outlets 90B or '90C'de-`l pending on which of the solenoids S3 or S4 is eii'e'rgised to draw the piston of the valve to the rightfor lett.

The outlets 90B and 90C are connected respectively by lines 91 and 92 tothe control'lports 1 0G and 100F at yopposite fends of a pressure operated`valve'1'00. This Valve has an inlet AA also in communication with' the pressure line 7-1 from the master controlvalve 70. Dependingon lwhich of the ports 100G and ltlilF are placed under pressureffr'om "the valve 90 the piston'of thevalve 100' will' move to theleft or right to plac`z'e`y'thev inlet 1100A' in communication with 'either the outlet` 100C or outlet 100B. In this way pressure will be transmitted to one or'other of the lines 101 or 102 whichjare respectively in communication with the lines y55 `and l56 to 'tl'ietmotoi 26.

' Accordingly, assuming the switch 8) tobefmoved to the Raise position, the contacts 81 will "be closed to energise the solenoid S3. This will draw the piston ofthe valve 90 to the left to place the outlet 90C of Y thisvalve in communication with the inlet-90A to supply pressure via the line 92 to the right hand end of the piston ofthe valve 100. This will4 accordin'glyber'rroved` to the leftV to place the outlet 100B in 'connection with the finletl 100A so thatl pressure is transmitted. via the' this'happensthe valve 90 is centred to cutoit the pressure; and accordingly the motor will bef from the vvalve 100 stopped..

To lower the adjustable roller again the switch 80 is moved to the Lower position to close the contacts 84. This energises the solenoid S4 to move the valve 90 in the opposite direction so that pressure is applied to the left-hand end of the valve 100 so that its inlet 100A and` outlet 106C are in communication and the pressure will be communicated via the lines 101 and 56 to operate the motor in the Lower direction. Assuming the switch 80 is maintained in the Lower position the roller arm is lowered until it engages and opens the limit switch 53 which open-circuits the solenoid S4 to stop this operation.

As will be seen in Figure 2 the diagrammatically shown brake is connected to the piston 19 of the cylinder 30 the lower end of which is connected to a two-way valve 111 the opposite ends of which are connected to the lines 55 and 56 running to the motor so that whenever pressure exists in one or other of these passages the pressure is applied to the lower side of the piston 19 to maintain the brake in an off position. When there is no pressure in either of the passages 55 and 56 however, the brake cylinder Si? is relieved and the brake applied by the spring 28.

What I claim as my invention and desire to secure by Letters Patent is: Y

l. Tensioning mechanism for an endless web including a jockey roller biassed onto the web to control its tension, an adjustable roller bearing on the web at another point, control means by which movement of the jockey roller out of a predetermined position relative to the web due to changes in the length of the web causes automatic operation of relay mechanism to move the adjustable roller relative to the web in such a direction as to adjust the web in a manner to restore the jockey roller to its predetermined position and manually-operable means for raising both jockey and adjustable rollers to remove the tension from the web.

2. Tensioning mechanism as claimed in claim l in which the adjustable roller is operated by a reversible hydraulic motor and the supply to the motor is under the control of a relay control Valve under the direct control of the jockey roller.

3. Tensioning mechanism as claimed in claim 2 including an overriding control for rendering the automatic relay mechanism inoperative when the manually operable means are in operation.

4. Tensioning mechanism as claimed in claim 3 in which the overriding control comprises a cut-ott valve between the reversible hydraulic motor and the relay control valve.

5. Tensioning mechanism as claimed in claim 4 in which the cutaoff valve is hydraulically operated by pressure derived from a solenoid-operated auto-control valve, means being included for raising the jockey and adjustable rollers hydraulically by pressure derived through a master valve, the solenoid of the solenoid-operated auto-control valve being in series with a cut-out switch, and the master valve being adapted when actuated to supply the raising means to operate the switch so as to cause the solenoid to actuate the auto-control valve and hence the cut-Dif valve to stop the hydraulic motor.

6. Tensioning mechanism as claimed in claim 2 including a directional control valve having two solenoids adapted to be energised alternately to operate the valve for actuating the hydraulic means in either a raising or lowering direction.

7. Tentionsing mechanism as claimed in claim 6 including a changeover switch having alternative pairs of contacts, one pair in series with one solenoid and thev second pair in series with the other solenoid.

8. Tensioning mechanism as claimed in claim 7 including #upper and lower limit switches in the solenoid circuits, the switches being adapted to open circuit their respective solenoids when the adjustable roller reaches predetermined upper or a predetermined lower position.

9. Tensioning mechanism as claimed in claim 1 in which the means for raising the jockey roller comprises a hydraulic piston.

l0. Tensioning mechanism as claimed in claim 9 in which the hydraulic piston is under the control of a. manually-operated jockey-roller-Control-valve.

11. Tensioning mechanism as claimed in claim 2 including a brake which is automatically applied to maintain the adjustment of the adjustable roller when the hydraulic motor is out of operation but released when the hydraulic motor is in operation.

References Cited in the tile of this patent UNITED STATES PATENTS 395,883 Dodge v Ian. 8, 1889 1,888,309 Cramer Nov. 22, 1932 2,797,075 Wilbur p June 25, 1957 

